1. Field of the Invention
The present invention generally relates to push-button tuners for radio receivers and more particularly to a push-button tuner in which two preset broadcasting frequencies can be selectively tuned in by each push-button.
2. Description of Prior Art
Widely known is a push-button tuner having a plurality of push-buttons each of which is set to tune in to a preset broadcasting frequency so that a desired broadcasting frequency is tuned in by depressing a selected one of the push-buttons into its actuated position. In such a push-button tuner, usually, only one broadcasting station could be selected by one push-button so that in order to tune in to a plurality of broadcasting stations by push-buttons, it has been required to provide a plurality of push-buttons corresponding in number to the number of the broadcasting stations. To increase the number of the push-buttons, however, it was necessary to enlarge the size of the tuner per se, and thus there was a limit as to the number of numbers of broadcasiting station by which could be selected using a small sized tuner.
Accordingly, there has been proposed a push-button tuner in which a pair of adjacent tuning members are provided with each push-button disposed therebetween and the selected one of the tuning members is interlinked with the push-button so that two different broadcasting stations can be selected by each push-button, whereby it is made possible to select a number of broadcasting stations which is two times as large as the number of push-buttons. For example, Japanese Utility Model Publication No. 21397/1982, which relates to an invention invented by the same inventor of the present application, discloses a push-button tuner which comprises a pair of tuning members located at the opposite sides of each push-button member and a change-over member for manually selectively changing over the tuning members to restrict the movement of the selected one of the tuning members. A mechanism for displacing a tuning member by means of movement of the the push-button member is constituted by a pinion rotatably mounted on the push-button member and a rack provided on the tuning member and meshed with the pinion. In order to displace a desired one of the pair of tuning members, the push-button member is depressed after the other tuning member has been fixed by the change-over member. Thus, the pinion moves, while rotating, along the rack on the fixed tuning member. At the same time, the desired tuning member is displaced by means of the movement of the push-button member and the rotation of the pinion.
The change-over member changes over the frequency band, for example, between an AM band and an FM band, in accordance with the change-over position thereof. Thus, the pair of tuning members disposed at the opposite sides of the push-button member are caused to tune in to different frequency bands respectively. Accordingly, it is necessary to operate the change-over member every time the tuning operation is changed from the AM band to the FM band, and vice versa. Even if five push-button members are provided to make it possible to tune in to ten radio stations, five of the stations are allotted for the AM band, while the remainder five stations are alloted for the FM stations. That is, it is impossible to effect such allotment that four and six stations are allotted for the AM and FM bands respectively.